The objective of this project is to investigate the immune functions of burn patients' mononuclear cells. Definition of the cell type(s) and the nature of burn induced immune defects will deliniate possible mechanism(s) by which thermal injury can compromise immunocompetence. The proposal focuses on possible burn induced aberrations in the interactions of Accessory cells (A cells) and Thymus-derived lymphocytes (T cells). Three different experimental systems are used to examine the effect of burns on A cell-T cell activity in immune response induction. The post burn A cell-T cell interactions in T cell proliferation are examined using a T cell mitogen response system. We will investigate the possibility that thermal injury induces increased suppressive or inhibitory A and T cells by utilizing a new adaptation of the mixed lymphocyte response (MLR). This same modified MLR system is employed to determine the target cell of burn induced suppressor cells. The effect of thermal injury on A cell facilitation of specific immune responses is probed in a system measuring the in vitro generation of specific antibody forming cells (AFC). A new method of inducing human peripheral blood mononuclear cells to produce specific AFC in vitro is described. Combining the information derived from our three experimental system will furnish a more complete characterization of the burn induced aberrations in A and/or T cell function which compromise burn patients' immunocompetence.